Warm, dry conditions inhibit aspen growth, but tree growth and size predict mortality risk in the southwestern US
Widespread, rapid aspen (Populus tremuloides) mortality since the beginning of the 21st century, sometimes called sudden aspen decline (SAD), has been documented in many locations across North America, but it has been particularly pronounced in the southwestern U.S. We investigated the relationship between aspen growth, mortality, and climate across three forest types in northern Arizona using crossdated tree-ring samples from 126 live and 132 dead aspen. Aspen growth was negatively correlated with warm temperatures and positively associated with higher precipitation. Using survival analysis techniques to investigate the links between aspen mortality, tree traits, and climatic conditions, we found that tree traits played a larger role in mortality risk than climate factors. Trees with larger diameters, older trees, and trees with faster growth rates over the past 50 years had a reduced risk of mortality. Management actions aimed at maintaining the most vigorous, fastest growing aspen in the region could help mitigate the impacts of a warmer, drier future.